In potato cultivars reacting non‐hypersensitively, systemic mosaic symptoms were obvious at 10‐20°C for potato virus X (PVX) isolate DX, and at 10 and 15°C for PVX isolate B: systemic movement was slowest at 10°C especially with DX. Viral antigen accumulation in non‐inoculated leaves was greatest at 15 and 20°C with B. but with DX accumulation was as great at 25°C, The highest viral antigen concentrations reached were less with B than with DX. No PVX was detected in plants grown at 30°C. In potato cultivars carrying gene Nx, necrotic local lesions appeared at 10‐25°C in DX‐inoculated lea ves within 8 days; systemic necrosis developed soon after at 15 and 20°C, but was very slow to appear or failed to develop at 10 and 25°C, Necrosis was more conspicuous when gene Nb was also present. Except at 10°C in the Nx:nb cultivar used, presence of Nx decreased accumulation of DX antigen. Although numerous necrotic lesions developed in B‐inoculated leaves at 10°C in the presence of gene Nb, very few formed at 15 and 20°C, and none at 25°C. In B‐inoculated leaves from plants at 15‐25°C, no new lesions were induced by temperature shock treatments and no starch lesion formation was detected. Gene Nb completely prevented movement of isolate B out of inoculated leaves at all temperatures regardless of whether infection was symptomless or necrotic local lesions developed, The concentration of B‐antigen was considerably decreased by Nb. It was possible to quantify the general effects of genes Nx and Nb on accumulation of DX‐ and B‐antigens: in the combination Nx:Nb the ineffective gene interacted with the effective gene to cause a greater depression of viral antigen accumulation than expected. Unlike hypersensitivity genes for tobacco mosaic virus in tomato and tobacco, Nx and Nb in potato did not lose their effectiveness with increasing temperature. Differences in virus accumulation and in temperature optima for multiplication between PVX strain groups may account for the lack of competitiveness shown by those belonging to group two.
|Number of pages||10|
|Publication status||Published - Dec 1986|